Tools and tool holders of various kinds have been developed which releasably retain a bit or other tool in place so as to enable different bits or tools to be used with the same device by simply substituting one tool for another. For example, power tools such as drills are provided with chucks which enable different drill bits (e.g., bits of different lengths and/or diameters) to be used. There are problems with many tools of this type with respect to the nature of retention or holding forces provided thereby. Some simple tools of this type do not provide any positive retaining forces other than those provided by the friction fit between the shank of the tool and the walls of the tool holding portion, whereas others, although providing positive retention, e.g., through the drawing together of the jaws of a chuck, require considerable manipulation to effect retention of a tool in place therein.
Some examples of tools and tool holders which provide positive retention forces through the use of retaining clips, spring-loaded dogs, detents and the like to hold a tool in place include those disclosed in the following patents: U.S. Pat. Nos. 1,469,792 (Johnson); 1,784,911 (Schlitters, Jr., et al); 2,410,971 (Hartley); 2,682,414 (Richardson); 2,736,562 (Blackburn); and 3,367,727 (Ward et al). Briefly considering these patents, the Hartley patent discloses a screw driver including a tool or bit having an annular groove therein adapted to be engaged by a retaining spring finger. The Richardson patent discloses a longitudinally adjustable screw driver including a tool having shank including receiver therein adapted to be engaged by the dog of a spring-loaded, pivoted retaining assembly. The Blackburn patent discloses a drill assembly wherein a ball is used to retain a tool in place. The Schlitters, Jr. et al patent discloses a tool retaining device including a detent which engages in a groove in the shank of a tool. The Ward et al patent discloses an oral surgery tool wherein interchangeable blades are held in place by a ball detent arrangement. The Johnson patent discloses a screw driver including a removable blade held in place by a U-shaped spring.